On Apr 19, 8:09*am, Cecil Moore wrote:
To make matters even worse: I had a similar problem
with drooping 1/4WL radials DC insulated from the tower.
The drooping radials coupled RF into the tower and
turned it into a radiator which screwed, oops, I
mean skewed the radiation pattern upwards.
________________

Some designs use drooping radials to reduce the vertical angle of the
peak radiation launched by the monopole section.

But that is a conclusion made for an infinite distance, with
consideration of the propagation environment on the intrinsic pattern
launched by the monopole, and the height of the monopole + its
elevated radials above the earth.

The link below leads to paste-up of NEC screens showing the
performance of a monopole driven against four 1/4-wave, essentially
horizontal radials. The entire system is isolated from earth ground.

The driving impedance, the elevation pattern shape, and the peak gain
are close to "textbook" values for a 1/4-wave monopole driven against
a perfect ground plane.

A form of this design is being used with good success in the AM
broadcast industry -- where using a conventional, buried-radial ground
system is impractical due to rocky terrain.

The groundwave performance of these systems shows that their intrinsic
gain is maximum in the horizontal plane, and very close to the
theoretical value of 5.15 dBi.

http://i62.photobucket.com/albums/h8...dRadials_1.jpg

RF

On Apr 19, 10:09*am, Richard Fry wrote:
On Apr 19, 8:09*am, Cecil Moore wrote: To make matters even worse: I had a similar problem
with drooping 1/4WL radials DC insulated from the tower.
The drooping radials coupled RF into the tower and
turned it into a radiator which screwed, oops, I
mean skewed the radiation pattern upwards.

________________

Some designs use drooping radials to reduce the vertical angle of the
peak radiation launched by the monopole section.

But that is a conclusion made for an infinite distance, with
consideration of the propagation environment on the intrinsic pattern
launched by the monopole, and the height of the monopole + its
elevated radials above the earth.

The link below leads to paste-up of NEC screens showing the
performance of a monopole driven against four 1/4-wave, essentially
horizontal radials. *The entire system is isolated from earth ground.

The driving impedance, the elevation pattern shape, and the peak gain
are close to "textbook" values for a 1/4-wave monopole driven against
a perfect ground plane.

A form of this design is being used with good success in the AM
broadcast industry -- where using a conventional, buried-radial ground
system is impractical due to rocky terrain.

The groundwave performance of these systems shows that their intrinsic
gain is maximum in the horizontal plane, and very close to the
theoretical value of 5.15 dBi.

http://i62.photobucket.com/albums/h8...WithElevatedRa...

RF